The invention relates to an image projection system comprising a projector for supplying a projection beam which is modulated with the image to be projected, an image projection screen and a folding system arranged between the image projector and the image projection screen, the folding system comprising a beam splitter for at least partly reflecting the projection beam from the projector, and a reflector for receiving the part of the projection beam reflected by the beam splitter and for reflecting said part to the beam splitter again.
An image projector is herein understood to mean a device which is provided with an image display system and optical means for projecting the image generated by this system on an image projection screen. The generated image may be a video image, a graphic image, data or a combination thereof.
An image projection system of the type described in the opening paragraph is known from European Patent Application 0 333 333 to which 4,969,732 corresponds. The image projection system described in this Application includes a beam splitter which passes substantially half the incident projection beam and reflects substantially half this beam to a reflector which is arranged at the same side of the beam splitter as the projector. After reflection on the reflector, half of the beam is passed by the beam splitter again and half of the beam is reflected again. A drawback of this image projection system is a relatively low efficiency, because only about 25% of the unpolarized radiation emitted by the projector is incident on the image projection screen.